Did you ever see a fat chimpanzee? Most people have a fair amount of fat tucked away, but you’ll seldom see a chimp with a spare tire. Even body builders have more fat than chimpanzees, to say nothing of the rest of us. Healthy men average 12–20 percent body fat, and women 24–31 percent. Male chimps, in contrast, carry almost no body fat, and females carry a lean 3.6 percent. The difference is present from birth. Human newborns have about 15 percent body fat compared to 3 percent for baby chimpanzees. God made us similar in many ways, so why the huge difference in body fat? The answer relates to our energy needs.
Compared to apes, humans are energy guzzlers. Even couch potatoes burn calories faster than apes. Our metabolic rate is 27 percent higher than a chimp’s. And we carry around extra fuel because we can’t afford to run out. Scientists think we consume so much energy because our brains are three times the size of a chimp’s. Our brains use 20 percent of the calories we burn, and God designed us to meet those high energy needs.
Because we burn energy fast, we often tap into the fuel stored in fat to carry us through to the next convenient meal. Apes, with smaller brains and slower metabolism, do not need to haul around a backup fuel supply. While some people pile on an unhealthy amount of fat through overeating and underexertion, the normal amount of body fat is our friend.
Pound for pound, fat stores more energy than other sorts of biomolecules like muscle protein, starches, and sugars.
God designed our bodies to store most of our surplus calories as fat. Pound for pound, fat stores more energy than other sorts of biomolecules like muscle protein, starches, and sugars. (Fat deposits also serve as internal shock absorbers and insulation.) So if you don’t like the shape of the fat you are storing, just imagine how much lumpier you would look if you had to store an equivalent amount of fuel as starch, which would take up much more space!
The body breaks down fat to obtain energy. However, while most organs—including resting muscle, the heart, and the liver—thrive on fatty acids, it may surprise you to learn that the brain is not directly fueled by fat. The brain demands glucose. The liver can transform only a small portion of each triglyceride fat molecule into glucose. But the fatty acids from fat breakdown keep our bodies going, and that spares glucose to fuel the brain and exercising muscles. If necessary, the body can make glucose by breaking down muscle. And during a long fast the brain adapts to accept fatty acids as fuel.
The body maintains a remarkable balance among the processes that break down and store nutrients from food, generate energy, and transform biomolecules into different forms as needed. These transformations involve a witheringly complex series of chemical reactions, all controlled by a network of specialized enzymes. Furthermore, the give-and-take way in which our tissues shift their fuel supplies to save glucose for the brain, and the brain’s ability to adapt to a secondary fuel source are both great examples of God’s wise design. These interconnected, finely tuned mechanisms clearly could not arise through the millions of random processes required by evolution.
An Improbable Tale
Evolutionary scientists believe an ape-like ancestor somehow developed a ramped-up metabolism to supply energy for the evolution of our large, energy-hungry brains. Some think human ancestors evolved bigger brains because they learned to cook their food, enabling them to consume more calories faster. Now evolutionists are claiming that the availability of fuel from stored body fat also helped the big human brain evolve. However, fat is not the primary fuel source for the brain.
In any case, these fanciful stories don’t address the root question. No amount of food, cooked or not, can supply an ape-like creature with new genetic information to evolve a complex human brain. Neither can a backup fuel source. God designed chimps to get along without stored fat. But he designed human beings differently, as his image-bearers. We need our dramatically higher metabolic rate to fuel the human brain God created. And with such high energy requirements, we need stored fat to keep us going while saving glucose for the brain.
We don’t want to spend all of our time eating, so we can be thankful God designed us to store fat. Nothing about the great designs for storing and using fat points to mindless evolution. Quite the contrary, these intricate, interrelated processes reveal the wise mind of our Designer and Creator.